1. The Field of the Invention
The present invention relates to a transmitter, a receiver and to corresponding methods for transmitting and receiving data utilizing sequences of non-return-to-zero, inverted (NRZI) symbols and symbol rates higher than the Nyquist rate in data transmission systems, thus enabling an enlarged spectral efficiency while utilizing simple transceivers (transmitters and/or receivers) which offer only lowest resolution in amplitude domain but enhanced resolution in time domain.
2. The Relevant Technology
In today's communication and data processing systems large amounts of information have to be handled. Especially the communication of huge streams of information is critical. Communications with data transfer rates of multiple gigabits per second are common. High requirements regarding communication speed and reliability necessitate complex transmission systems and methods, which are capable of transmitting fast and reliably such large amounts of information. Such information in form of data has to be transmitted between different systems and units. Hereby, radio transmission is a particular demanding field, due to addition-al sources of interference that add to the transmitted data signal. In order to cope with the high requirements in radio data transmission many different transmission strategies have been developed.
These strategies are based on different signal processing methods, wherein the information or payload data is processed before transmission in a transmission system and recovered at a receiving system. In the past more and more complex encoding and modulation methods were developed due to the rising volume of data to be transmitted. Usually the spectral efficiency is increased by introduction of a more complex modulation alphabet (more symbols). The different symbols of a modulation alphabet vary in phase, amplitude and/or frequency. A very successful representative is the Quadrature Amplitude Modulation (QAM) scheme. At the receiver a sampling unit comprising an analog-to-digital converter (ADC) can be deployed for digitizing a receive signal for further processing.
As a general rule, more complex modulation alphabets result in increased requirements for the ADC. According to the Nyquist-Shannon sampling theorem such ADCs must sample a received analog signal with a sampling frequency which is at least twice the maximum frequency of the received signal. The thusly defined minimum sampling rate is also known as Nyquist rate for sampling. At high sampling rates ADCs with high resolution in amplitude of a signal are difficult to realize and have a high power consumption.
These highly developed converters are a particularly cost intensive factor in receiver systems and the enormous power consumption of such ADCs is a critical drawback, particularly in receiver systems having a limited power source such as a battery, an accumulator and the like.
Consequently, a system and method for fast and reliable transmission of data without expensive and energy intense hardware components, especially at the receiver side, is desirable
Hence, it is an objective of the present invention to solve or alleviate the technical problems and disadvantages inherent to the prior art and as set forth above. The present invention describes a transmitter and corresponding receiver for transmitting and receiving high speed data streams with energy efficient hardware components, especially at the receiver end.